1. Field of the Invention
The present invention relates to a transmission apparatus and a transmission method, and is particularly favorable for use in a transmission apparatus for transferring data to be transmitted and received by packet communication.
2. Description of the Related Art
Conventionally, in packet communication, time information (hereinafter, called “time stamp”) is given to each packet to be transferred, and packet transfer is carried out from a transmitting end to a receiving end, in consideration of handling of packet loss in a transmission line and transmission delay. In the receiving end, the packets are read out and reproduced in accordance with the time stamp given to the packets, and thereby intervals between the packets at the time of transmission are reproduced (for example, see Patent Document 1).
However, when the time stamp is given to each packet to be transmitted, if real time date (bit stream), which is demanded of real time property, such as voice date and image data is transferred by packet communication, the time stamp amount becomes overhead, which results in reduction in transmission efficiency. For each packet, processing of giving the time stamp is performed in the transmitting end and readout and reproduction processing is performed in the receiving end, thus causing reduction in processing speed and bloating of the circuit scale.
As one of the methods for solving the above-described problems, there is proposed a method for reducing a transmission and reception data amount per one data packet by bringing a plurality of time-series data packets together as one group, giving a time stamp for each group and transferring them (for example, see Patent Document 2). In the method proposed in the Patent Document 2, in the transmitting end, one of the data packets in the group is specified and given the time stamp of the data packet, and the group is transferred to the receiving end. In the receiving end, the readout timing of the data packets in the group is controlled and reproduced based on the given time stamp.
However, in the method proposed in the Patent Document 2, the readout timing is controlled by estimating the periods of the data packets based on the given time stamp and the number of data packets included in the group, and therefore the data packets which are reproduced in the receiving end have to have time-series arrangement in a certain fixed period in the transmitting end. Accordingly, the aforementioned transmission method cannot be applied to the case in which the data packets to be transferred exist at arbitrary time intervals.
[Patent Document 1] Translated National Publication of Patent Application No. 2002-524981
[Patent Document 2] Japanese Patent Application Laid-open No. Hei9-298558